U.S. Pat. No. 4,971,068 discloses a needle comprising a metal cannula and a temperature sensitive indicator mounted on the cannula. Blood vessel penetration is visually indicated by a change of color of the temperature sensitive indicator in case blood enters the cannula and reaches said temperature sensitive indicator.
A problem of the needle disclosed in U.S. Pat. No. 4,971,068 is that it is not capable of monitoring whether or not the cannula maintains a positioning inside the blood vessel during infusion procedures, i.e. procedures in which a liquid is supplied to the patient. Namely, the needle disclosed in U.S. Pat. No. 4,971,068 requires blood itself to flow into the cannula up to the temperature sensitive indicator in order to observe blood vessel penetration hence to observe the positioning of the cannula in the blood vessel.